Low-temperature magnetic properties of NpNi5

A. Hen, E. Colineau, R. Eloirdi, J. C. Griveau, N. Magnani, F. Wilhelm, A. Rogalev, J. P. Sanchez, A. B. Shick, I. Halevy, I. Orion, R. Caciuffo

Research output: Contribution to journalArticlepeer-review


We present the result of an extended experimental characterization of the hexagonal intermetallic Haucke compound NpNi5. By combining macroscopic and shell-specific techniques, we determine the 5f-shell occupation number nf close to 4 for the Np ions, together with orbital and spin components of the ordered moment in the ferromagnetic phase below TC=16 K (μS=-1.88 μB and μL=3.91 μB). The apparent coexistence of ordered and disordered phases observed in the Mössbauer spectra is explained in terms of slow relaxation between the components of a quasitriplet ground state. The ratio between the expectation value of the magnetic dipole operator and the spin magnetic moment (3Tz/Sz=+1.43) is positive and large, suggesting a localized character of the 5f electrons. The angular part of the spin-orbit coupling (- ·s- =-5.55) is close to the value of -6.25 calculated for trivalent Np ions in intermediate coupling approximation. The results are discussed against the prediction of first-principle electronic structure calculations based on the spin-polarized local spin density approximation plus Hubbard interaction, and of a mean field model taking into account crystal field and exchange interactions.

Original languageAmerican English
Article number054408
JournalPhysical Review B - Condensed Matter and Materials Physics
Issue number5
StatePublished - 11 Aug 2014

All Science Journal Classification (ASJC) codes

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics


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